A quantitative description and understanding of the role of hemo-dynamic stress in altering vessel wall morphology and in the pathogenesis of arteriosclerosis is sought, with particular emphasis on the quantitative fashion in which arterial geometry influences the hemodynamic stresses on susceptible arterial segments. Human coronary arteries and branches and aortic bifurcations selected in accordance with these objectives, will be studied grossly and by light microscopy; these vascular segments will include normals and those with varying tortuosity, branch-point geometry and intimal disease. A transparent plastic cast will be made of selected segments of interest, and the morphological observations will be compared in detail with local hemodynamic measurements in the cast; the hemodynamics will be measured noninvasively by laser Doppler velocimetry. From correlations of local hemodynamic stress and tissue response an attempt will be made to identify geometric risk factors which could contribute to arteriosclerosis.